1. Field of Invention
The invention relates to synchronization of signals, and more specifically to a circuit and method for synchronizing an asynchronous signal with a synchronous, on-demand, oscillating signal.
2. Discussion of Related Art
In processor applications it is often desirable, or even necessary, to synchronize actions performed at a first clock frequency with actions performed at a second clock frequency. For example, read and write operations from registers may be performed at different speeds. For instance, the register may be written to, or updated, once every second, while the circuitry that reads from the register and manipulates, decodes, stores, or otherwise operates on data in the register may be controlled by a clock signal of higher frequency, for example 100 MHz. In such a situation, the circuitry controlled by the 100 MHz clock may complete the manipulation of the data in the register in advance of the register being updated again. If the circuitry controlled by the 100 MHz clock were to continue to read data from the register and manipulate the data, its operation would be redundant, since the register had not yet been updated with new data.
Worse, the continuous operation of the 100 MHz circuitry would be inefficient, since circuits that produce, or are controlled by, oscillating signals often consume power during operation; namely, in the process of changing the state of a signal from low to high, or vice versa. Therefore, circuits which produce, or are controlled by, an oscillating signal with a high frequency are likely to consume more power than a comparable circuit producing, or operating under the control of, an oscillating signal with a low frequency. In effect, substantial power may be consumed in continuously producing a high frequency oscillating signal, despite the fact that the signal is only needed for a portion of the time it is being run. As processor clocking speeds continue to increase, this amount of power will likely increase as well. Thus, efficient circuits and methods for synchronizing an asynchronous signal with an on-demand synchronous signal are needed.